Heat-exchanger tube



1944- J. w. BROWN, JR ETAL I ,1

HEAT EXCHANGER TUBE Filed Aug. 7, 1941 INVENTORS 1/0H/v W. Bean/N v2.WILL/AM C. JE-5lS/0N6 A True/wens:

Patented Feb. 22, 1944 'HEAT-EXCHANGER TUBE John W. Brown, Jr., andWilliam 0. Sessions, Lakewood, Ohio, assignors to Brown Fintube Company,Elyria, Ohio, a corporation of Ohio Application August 7, 1941, SerialNo. 405,836 4 Claims. 01. 257 2c2 This invention relates to theconstruction of heat exchange devices and more particularly to surfacesprovided with fins for increasing the surface area thereof and thusincreasing the heat transfer capacity of the surface. The invention isdescribed herein with particular reference to finned tubes, but it is tobe understood that the invention may be employed with other forms orshapes of surfaces. The prior application of John W. Brown, Jr., SerialNo. 386,503, filed April 2, 1941, discloses a tube and method andapparatus for making the same wherein channel section members are weldedto the exterior of the tube and the flanges of the channel subsequentlyare brought into contact with each other to make the two flanges into asingle fin. These tubes have very advantageous characteristics, butunder some circumstances of particularly severe operating conditions thetemperature gradient between the tips of the flanges or fins and thetubemay be so great that the outer portions of the flanges or fins arenot efficient from a heat transfer standpoint, and under somecircumstances where very hot gases are on the exterior of the tubes thetips of the fins may be heated to such an extent that they will bedamaged or burned.

It is an object of the present invention to overcome these diflicultiesand to provide finned tubes or other members and a method of making thesame whereby the temperature gradient between the tips or outer edges ofthe fins and the bases may be kept within reasonable bounds and. whereindirect and adequate paths are provided for the transfer of heat from thetips of the fin's to the bases thereof. It is a further object of ourinvention to provide such fins which can be rapidly and economicallymanufactured,

and another object is to provide an eflicient and economical method formanufacturing such finned members.

Briefly, we accomplish the above and other objects of our invention bysecuring to the tube, or-other surface, one or more hollow fins, andproviding heat conducting members extending within the hollow fins fromthe tip or edge portions thereof to the base portions thereof. By thismeans, a direct path for the flow of heat from the tip to the base ofthe fin is provided which is particularly eflicient, for the metal heatconducting member, being spaced apart from the side walls of the finthroughout a considerable portion of its length, can receive heat byconduction only from the base of the fin or the tip. By thisconstruction the temperature cient in transferring heat and damage tothe.

fin under severe operating vented. 1

Preferably, we produce such hollow fins by welding, brazing or otherwisejoining to the exterior surface of the tube, or other member, twochannel section members, each having a base portion and two flanges withthe base portions of both in engagement with the tube and one flange ofone channel member in engagement with a flange of the other channelmember. This operation produces a structure with four projecting fins,the two inner fins lying alongside of each other and the two outer finsbeing spaced therefrom. Preferably, the welding operation is carried outas described in detail in the application of John W. Brown, Jr., SerialNo. 380,690, filed April 2, 1941, thus providing adequate paths for thetransfer of heat from the bases of the channel members to the tube.

After the channels have been welded to the tube or other member, theouter flanges of each pair of channels are bent into engagement withconditions is prethe inner flanges of the channels adjacent their outeredges and the four flanges are then welded together preferably either bya continuous weld or a. series of spot welds, in a zone spaced away fromthe bases of the channels and near the outer edges of the flanges. Thisproduces a structure wherein the supporting member is provided with ahollow fin welded to its surface, the outer lateral surfaces of the finbeing formed by the outer flanges of the two channel members, the tip ofthe fin being solid and being formed by the four flanges weldedtogether. The heat conducting member for rapidly transferring heatbetween the base of the fin member and the tip is formed by the twoinner flanges which, being disposed'within the hollow portion of thefin, can receive or dissipate heat by conduction only from or to the tipof the fin or the base portion thereof. Because heat will seek the pathof least resistance, the centralconducting member may conduct heat fromor to the lateral surfaces of the fin, but the flow will be largelythrough the tip portion. The two channel members may be separatelyformed or they may be formed in' 386,503 aforesaid, and modified as willbe described in detail below.

Referring now to the drawing in which the invention is described, withparticular reference to finned tubes, Fig. 1 is a perspective of apreferred form of finned tube made according to our invention andembodying longitudinally extending fins on diametrically oppositesurfaces of the tube; Fig. 2 is a fragmentary view illustrating one stepin the manufacture of the tube of Fig. 1; Fig. 3 is a similar viewshowing a subsequent step in the manufacture of the tube of Fig. 1; Fig.4 is a somewhat diagrammatic sectional view illustrating the operationof welding opposite pairs of channel members to a tube; Fig. 5 is aperspective of a slightly modified form of our invention showing a tubeembodying longitudinally extending fins on diametrically oppositesurfaces of the tube; and Figs. 6 and 7 are fragmentary viewsillustrating steps in the manufacture of the tube shown in Fig. 5.

As illustrated in Fig. 1 of the drawing, a preferred form of ourinvention may comprise a tube l having fin members indicated generallyat H secured to the exterior thereof at diametrically opposite points.Each fin member is made up of two channels indicated generally at [2 andI4 in Fig. 2, the channel I! having a base portion l5, and flanges l6and I1, and the channel l4 being similar in all material respects andhaving a base portion 18 and flanges l9 and 20. To produce the hollowfin structures ll shown in Fig. l, the channel members l2 and M areplaced along the tube ID with their base portions l and I8 in contacttherewith and with the flange H of the channel ii in engagement with theflange l9 of the channel I4. Then the base portions of the channels arewelded to the tube as indicated diagrammatically at 2| and 22,preferably as disclosed in the aforesaid Brown applications.-

Thereafter the outer flanges l6 and 20 of the channels l2 and M,respectively, are bent inwardly into engagement with the inner flangesl1 and IS, the operation being carried out preferably so that theflanges are in contact at their outer edges for a short space inwardlyand are spaced apart to leave hollows 23 and 24 as shown in Fig. 3. Theoperation of deforming the flanges for example, by rolls of the generalcharacter shown in the Brown application Serial No.

of heat from the fins to the tube as described in the aforesaidapplications. The diametrically opposite electrodes, that is, electrodes3| and 34, and.32 and 33, respectively, are of opposite polarity at anygiven instant to provide the required flow of current and thesimultaneous production of the welds.

It will be noted that the fins II have substantially flat surfaces attheir outer edges. This is accomplished by making the channels withtheir outer flanges l6 and 20 slightly longer than the inner flanges l1and I9 so that when the flanges l6 and 25 are bent into engagement withthe flanges l1 and I9,- the edges of all four flanges will substantiallycoincide. This type of construction is desirable for certain purposesparticularly where it is desired to abut the flanges of a number oftubes to form a wall.

In Figs. 5, 6 and 7 we have shown a slightly modified form of ourinvention wherein the tube 50 is provided with a pair of fins 5| whichare generally similar to the flns ll except that as shown in Fig. 6 thechannels 52 and 54 are made in one piece, being joined at 53 adjacentthe outer edges of the flanges 51 and 59. The base portions 55 and 58 ofthe channels in this modimay be carried out in any convenient manner,

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386,503, aforesaid. The tube may then be completed by welding thecontacting portions of the flanges l6, l1, I9 and 20 together,preferably by an electrical resistance weld indicated diagrammaticallyat 25 in Fig. 1, which may either be a continuous weld or a series ofspaced spot welds.

In welding the channels to the tube, we prefer that oppositely disposedchannels be welded simultaneously so that the heating effects on theopposite sides of the tube will be uniform and f for transferring heatthrough the hollow fins bebending or deformation of the tube prevented.

This operation may be carried out as indicated diagrammatically in Fig.4 wherein the tube I5 is supported and held in accurate position by apair of guide rolls 30 engaging the outer surface of the tube whileelectrode rolls 3|, 32, 33 and 34 engage the bases of the fins. The tubeis moved relative to the electrode rolls and the guide rolls and currentcaused to flow, simultaneously welding the bases of the four channelmembers to the exterior of the .tube. The current is preferablycontrolled to produce a series of intermittent welds having areas andcontours to provide adequate paths for the transfer fication may bewelded as described above, using welds indicated diagrammatically at 6|and 62. After the welding operation the outer flanges 56 and 50 may bebent into engagement with the inner flanges 51 and 59 in the mannerpreviously described, producing the structure shown in Fig. 7,preferably leaving spaces or hollows 53 and 54 in the fin. Thereafter,the tube may be completed by welding the engaging portions of theflanges together. as indicated diagrammaticallyat 55 in Fig. 5.

It will be noted that in this modification the joined portion 53 of theinner flanges 51 and 53 projects beyond the edge portions 56 and 61 ofthe flanges 52 and 54, for the flanges 56, 51, 53 and 60 are all of thesame length so that when the flanges 56 and 60 are bent into engagementwith the inner flanges 51 and 59, the edges thereof do not extendradially outwardly as far as the edge portion 53 of the inner flanges.Of course, a structure with a generally flat edge as indicated at 26 inFig. 1 may be produced with a tube made according to this modificationof ourinvention merely by making the'outer flanges 52 and 55 of slightlygreater lengthto compensate for the bending operation. Similarlychannels l2 and I4 of Fig. 1 may be made with flanges of equal length sothat when the outer flanges l6 and 20 are bent inwardly, an edgestructure would be produced in which the inner flanges project beyondthe outer flanges.

In both modifications of our invention the mner flangesconstitute heatconducting members tween the tube and the tipsor outer edges of thefins, for the inner flanges are in heat conducting relationship with thebases of the channel members which constitute the bases of the fins andwith the outer flange members adjacent the outer edges thereof. Thus, adirect path is provided which will insure suflicient transfer of heatbetween the tube and the outer edges or tips of the fins, will result ina lowered temperature gradient between these two regions, will improvethe heat-transfer ability of the fins, and will give the fins theability to withstand exceptionally severe operating conditions withoutdamage. This makes possible the construction of heavy- Those skilled inthe art will appreciate that various changes and modifications can bemade in our invention without departing from the spirit and scopethereof. For example, fins of this type may be employed with surfaces of-sup-' porting members other than tubes, diflerent methods of securingthe flns to the tubes or other supporting member maybe employed, the flnmembers may be oi. different shape, the steps oi. the method may becarried out in other than the preferred order. Therefore, it isto beunderstood that the foregoing description oi preferred forms is given byway of example and not by way of limitation, and that our patent is notlimited thereby or in any manner other than by the scope of the appendedclaims. I

We claim:

1. In combination, a tube, a pairof channel members each having a baseportion and flange portions, the base portions of said channel membersbeing resistance welded to the tube adjacent each other, the inner twoflanges of the channels being substantially. in contact with each otherand the outer flanges being bent inwardly into engagement with saidinner flanges and secured thereto in a region spaced away from said baseportions.

2.4L heat exchange conductor comprising a 2,342,117 duty fins from lightgage stock, reducing the tube, a double channel section member havingtwo base portions, a pair of outer flanges extending therefrom and aninner flange extending from the base portion between the outer flanges,

the base portions beingwelded to the tube by a seriesoi resistancewelded areas, the outer flanges being bent into contact with saidinnerflange,

' and said outer and'inner flanges being welded together.

3. In combination, a. supporting *member, a V

pair or channel members each having a base portion and two flangePortions, the base portions of said channel members being secured to thesupporting member adjacent each other, the inner two flanges or thechannels being substantially in contact with each other and the outerflanges being bent inwardly into contact with the inner flanges, thetour flanges being secured togetherin a region spaced away from saidbase portions. r

.4. A heat exchange conductor comprising a supporting member, a doublechannel section member having two base portions, a pair of outer flangesextending therefrom and an inner flange extending from the base portionbetween the outer flanges, the base portions being secured to thesupporting member, the outer flanges being bent into contact with saidinner flange, and said outer and inner flanges beinglsecurecl together.

' JOHN W. BROWN, JR. WILLIAM C. SESSIONS.

